In the manufacture of decorative sheet-type covering material such as sheet vinyl floor and wall coverings, it is frequently desired to provide a product which has a foamed vinyl layer on top of which is a PVC wear layer which in turn is covered with a polyurethane wear layer. The polyurethane wear layer serves to provide high gloss and the PVC wear layer to increase the useful life of the product if the polyurethane wear layer should wear through in spots. Previously such material has been made by first forming a conventional product having a foamed layer with a cured PVC wear layer and subsequently applying and curing the polyurethane wear layer on top of the previously cured PVC wear layer. This method of manufacture has effectively precluded the use of chemical embossing of the type described for instance in U.S. Pat. No. 3,458,337 since efficient coating with the relatively thin polyurethane wear layers used is possible only by the use of reverse or direct roll coaters. Other methods of application of the polyurethane finish are less desirable than roll coaters for various reasons. Losses from spray application are relatively very high. Air-knife systems introduce solvent fume disposal problems and certain coaters have not proven practical in maintaining acceptable thickness levels on wide sheets. Roll coaters, however, function best on level surfaces. In practice use of roll coaters to apply the polyurethane wear layer has required that the polyurethane layer be applied before embossing of the material. This has, in conventional methods of manufacture, precluded the use of chemical embossing and mandated that any embossing be via mechanical procedures.
A further disadvantage in conventional methods of manufacturing urethane coated foamed sheet covering materials has been the fact that wrinkling of the urethane layer has been encountered if the urethane layer is applied to a freshly cured PVC wear layer. This has frequently required storage of material to which a PVC wear layer has been applied and cured for a period of two to three weeks before a polyurethane wear layer could be applied without danger of wrinkling of the polyurethane layer during curing thereof.